Both 1,4-butanediol and tetrahydrofuran are useful as a solvent and raw materials for organic synthesis such as polymeric material. They have been produced through various ways. For example, tetrahydrofuran is produced by (a) catalytic hydrogenation of furan which has been obtained by elimination of carbonyl group from furfural, (b) dehydration cyclization of butanediol obtained by hydrogenation of butynediol which is a reaction product of acetylene and formaldehyde and (c) reaction of 1,4-diacetoxybutanediol and water in the presence of an acid catalyst; and 1,4-butanediol is produced by (d) hydrogenation of butynediol and (e) hydrolysis of 1,4-diacetoxybutane.
The production of 1,4-butanediol by hydrolysis of 1,4-diacetoxybutane and the production of tetrahydrofuran by cyclization of 1,4-diacetoxybutane with elimination of acetic acid belong to entirely different category of reactions as follows. ##STR1##
Thus, hitherto in producing 1,4-butanediol and tetrahydrofuran from 1,4-diacetoxybutane, both reactions have been carried out in separate reaction systems.
It has been found that, in the case where 1,4-butanediol and tetrahydrofuran are produced from an acetate ester of 1,4-butanediol in a single reaction zone containing a solid acid catalyst, the proportion of 1,4-butanediol and tetrahydrofuran is closely correlated with the reaction temperature, the liquid hourly space velocity (LHSV) of the acetate ester of 1,4-diol supplied to the reaction zone, the amount of the reaction product to be supplied to distillation column from which the 1,4-diol product is recovered and the amount of the reaction product to be circulated to the reaction zone. For example, the higher the reaction temperature, the higher the reaction rate at which the hydrofuran is produced; at a lower reaction temperature such as at 50.degree. C., the production of hydrofuran increases with an increase in the LHSV, and with an increase in the amount of the reaction product to be supplied to the separation column the amount of 1,4-diol product increases.
However, the hydrolysis reaction for producing 1,4-diol is preferably carried out with a high water content; on the other hand, the cyclization reaction is conveniently effected with a low water content. Thus, it is difficult to conduct two such different types of reaction in a single reaction zone at high efficiency.
It has been found that hydrolysis of 1,4-diacetoxybutane and cyclization of 1,4-diacetoxybutane with elimination of acetic acid can be carried out in separate reaction zones by circulating unreacted raw material recovered from each of the reaction zones to another zone, whereby the desired diol and cyclic ether are obtained with high efficiency and in any proportion, since the proportion may readily be changed as required.